JPH07336209A - Source coupling type current mode multi-value integrated circuit - Google Patents

Abstract

PURPOSE:To add a storage function to a threshold detector by attaining a high speed for the threshold detector being a basic circuit of a current mode multi-value integrated circuit to realize the current mode multi-value of high performance. CONSTITUTION:A switch circuit 24 in a threshold detector is made up of a source coupling circuit using a differential pair 22 and is operated by complementary signals on two lines. Furthermore, a storage use path transistor(TR) 25 or path gate is inserted between a comparator circuit 23 and the switch circuit 24 and a fan; storage function is provided for the threshold detector by the principle of dynamic storage of a binary CMOS circuit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of constructing a multi-valued logic circuit for the purpose of speeding up, densifying and reducing power consumption of a digital system in information processing.

[0002]

2. Description of the Related Art Current digital systems based on Boolean algebra have attempted to improve information processing capability by miniaturizing semiconductors and integrating them on a large scale. Along with this, physical limitations of integrated circuit technology, such as performance degradation due to an increase in the amount of wiring, are inevitable.

A system configuration based on multilevel information processing is being researched as a method for essentially solving such a problem.

The multi-valued integrated circuits proposed so far are
By engraving multi-bit information on one line by dividing the voltage and current into multiple levels, the wiring amount and the number of active elements can be reduced. This was a cause of performance deterioration such as increased delay time at the wear level.

[0005]

In the submicron integrated circuit, lower power supply voltage is required. Along with this, the further decrease in the logic amplitude accelerates the performance deterioration of the multilevel integrated circuit.

It is an object of the present invention to construct a multivalued integrated circuit which operates at high speed without lowering the current driving capability of the active element even if the logic amplitude decreases.

As a result, the advantages of the architecture, algorithm, etc. based on multi-valued expressions can be fully utilized, and the multi-valued integrated circuit technology makes it possible to achieve higher performance of digital systems.

[0008]

In a current mode multi-valued integrated circuit, a logical value corresponds to a current value.

A threshold detector, which is one of the components of the current mode multilevel integrated circuit, determines the performance of the entire circuit.

The threshold detector is a circuit corresponding to the basic element of the threshold logic for identifying and reproducing a multi-level current value.

FIG. 1 shows the circuit configuration of a conventional threshold detector. In the figure, x, y, T, m
Represent the current values of the input (1), the output (2), the threshold current source (3) and the output current source (4), respectively. The threshold detector has the function of satisfying the following relationship.

[Equation 1]

A threshold detector of a source-coupled current mode multi-valued integrated circuit of the present invention (hereinafter referred to as a two-wire threshold detector) has a circuit configuration shown in FIG. The two-wire threshold detector is composed of a source-coupled circuit using a two-wire complementary signal and using a differential pair (12) as a switch circuit, and has a function of satisfying the following relationship.

[Equation 2]

Further, as shown in FIG. 3, the comparison circuit (1
By providing the storage pass transistor (17) or the pass gate between the switch circuit (16) and the switch circuit (16), the storage function can be retained and a sequential circuit can be realized.

If the method of adding the above-mentioned storage function is applied to the two-wire type threshold detector,
The threshold detector having the high-speed and storage function shown in FIG. 4 can be configured, and a high-performance source-coupled current-mode multilevel integrated circuit can be realized.

[0015]

The two-wire threshold detector is capable of high-speed switching. Hereinafter, the principle of high speed will be described in comparison with a conventional threshold detector.

An equivalent circuit of the comparison circuit (6) is shown in FIG.
C in the figure is the gate capacitance of the control pass transistor (5) and the like. From this equivalent circuit, the following relational expression holds.

[Equation 3] However, dV and dt represent the minute voltage change and minute time change of V, respectively.

Further, in this circuit system, the charging time is generally longer than the discharging time, and therefore the delay time t of the threshold detector is obtained as follows.

[Equation 4] Here, Voff is the lowest voltage at which the output current becomes 0 in the characteristics of the switch circuit shown in FIG.

FIG. 7A shows a general example of a switch circuit (7) in which the output current source (4) is realized by a depletion PMOS transistor. The characteristics of each transistor are shown in FIGS. 7B and 7C. Where Vt
u and Vt are threshold voltages of the depletion and enhancement PMOS transistors, respectively. Vm is Vgs when the drain current is m.

In order to set the output current value y to 0, the respective transistors must be turned off at the same time, and the following relational expression must be satisfied.

[Equation 5]

From this, Voff is expressed by the following equation.

[Equation 6]

Therefore, from the equation (4), the delay time t of the threshold detector is expressed as follows.

[Equation 7]

Since the respective transistors must be turned on at the same time when the output current value is m, the following conditions must be satisfied.

[Equation 8]

Therefore, Von is expressed by the following relational expression.

[Equation 9]

FIG. 8 shows a circuit configuration of a two-wire type threshold detector using a depletion PMOS transistor as a current source. Each depletion and enhancement PMOS transistor is assumed to have the same characteristics as the transistor in a conventional threshold detector.

Here, in the characteristics of the switch circuit of FIG. 6, Von and Voff of the two-wire type threshold detector are shown.
Where Von 'and Voff' are newly defined, the following relational expressions are satisfied.

[Equation 10] In the above equation, one transistor of the differential pair (26) has a current m.
It is shown that the minimum value of the gate voltage difference between the respective transistors should be Vm-Vt when the other is cut off.

Here, assuming that Von 'is equal to Von, Voff' is obtained from the equations 9 and 10 as follows.

[Equation 11]

Therefore, the delay time t'of the two-wire type threshold detector is obtained from the equation 4 as follows.

[Equation 12]

As a result, at the same logic amplitude as before,
The two-wire threshold detector is C ・ Vtu / (T-
The delay time can be reduced by x).

The differential pair (1) of the switch circuit (14)
Since complementary signals can be taken out simultaneously from 2), it is also effective in reducing the number of active elements.

As described above, the PMO is used for the current source and the pass transistor.
Although the threshold detector using the S transistor has been described, it can be configured with an NMOS transistor. In this case, since the mobility of the NMOS is higher than that of the PMOS, further speedup can be expected.

Next, a method of adding a storage function to the threshold detector will be described. In FIG. 1, a threshold detector comparison circuit (6) outputs the magnitude relation between the current values of the threshold current source (3) and the input (1) as a binary voltage.

Therefore, dynamic storage in a normal binary CMOS circuit can be used, and a latch function can be added by simply inserting a storage pass transistor (17) or a pass gate as shown in FIG.

It is difficult to store the information expressed by the normal current, and the hardware overhead tends to increase, but in this case, the memory function can be added with very small hardware, and the sequential circuit can be simplified. Can be configured.

Further, when it is applied to a two-wire type threshold detector as shown in FIG. 4, since it is a differential input, the influence of the threshold voltage drop of the storage pass transistor (25) can be reduced, and high speed can be maintained. I also have

[0035]

FIG. 9 shows a basic circuit necessary for constructing a source-coupled current mode multilevel integrated circuit of the present invention. The current source and the threshold detector are shown in the case of using PMOS transistors.

The logical values of the two-line complementary signals are x,
Expressed as x ′, if the part has an R value, the following relational expression is satisfied.

[Equation 13] Here, + and-indicate addition and subtraction in the arithmetic operation.

The current mode multi-level integrated circuit has a linear addition (2
Since 7) can be realized only by wiring, it is effective for application to arithmetic operation systems. There are various applications such as image processing and signal processing.

Further, appropriate multi-level code assignment is performed, and the differential pair (12, 2) of the switch circuit (14, 24) is assigned.
By considering an appropriate combination with respect to 2), the arithmetic operation can be simplified and a high-performance logical operation circuit can be realized.

[0039]

The source-coupled current-mode multilevel integrated circuit of the present invention can realize a high-performance digital system that operates at high speed even if the logic amplitude is small. That is, it can be applied to all digital information processing systems and can contribute to the realization of high-performance integrated circuits.

Further, this feature can be maintained even when the power supply voltage is lowered.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram of a conventional threshold detector.

FIG. 2 is a circuit configuration diagram of a two-wire threshold detector.

FIG. 3 is a circuit configuration diagram of a threshold detector to which a storage function is added.

FIG. 4 is a circuit configuration diagram of a two-wire threshold detector to which a storage function is added.

FIG. 5 shows an equivalent circuit of a comparison circuit.

FIG. 6 shows the general characteristics of a switch circuit.

FIG. 7 shows a circuit configuration diagram (a) of a conventional threshold detector using a PMOS transistor, and general characteristics (b) and (c) of each transistor.

FIG. 8 is a circuit configuration diagram of a two-wire type threshold detector when a PMOS transistor is used.

FIG. 9 shows a basic circuit that constitutes a source-coupled current mode multilevel integrated circuit.

[Explanation of symbols]

 1, 8, 18 Inputs 2, 9, 19 Outputs 3, 10, 20 Threshold Current Sources 4, 11, 21 Output Current Sources 5 Controlling Pass Transistors 6, 13, 15, 23 Comparison Circuits 7, 14, 16, 24 switch circuit 12, 22, 26 differential pair 17, 25 storage pass transistor 27 linear addition

Claims (2)

[Claims] 1. A switch circuit (7, 14, 16, 24)
Is a source-coupled circuit having a differential pair (12, 22, 26), and is a two-wire threshold detector that operates at high speed using a two-wire complementary signal. 2. A threshold detector comprising a comparator circuit (6, 13, 15, 23) and a switch circuit (7, 1).
4, 16, 24) between the storage pass transistors (1
7, 25) to provide a storage function.